Adjusting device for endless chains



Nov. 21, 1939. J. H. wlLsoN ADJUST-ING DEVICE FOR ENDLESS CHAINS Filed June 2l, 1938 mill l i'iinnw.

Patented Nov. 21, 1939 UNITED STATES PATENT OFFICE 6 Claims.`

This invention relates to adjusting devices for endless chains, and is particularly adapted for adjusting endless chains used for driving certain types of mechanism, such as deepI well pumps and the like, in which the driving mechanism is called upon to exert rst a driving force and then a resisting force, so that one or both reaches of the chain become alternately slack and taut. However, the device of the present invention is not 10 restricted to use with such mechanisms, but may be advantageously used in connection with most chain drives, whether the power transmitted is constant or variable.

Chain adjusting devices employing movable bearings, and means actuated in accordance with 'the slackness of a reach of a chain for adjusting said bearings, are known, such devices usually comprising a member arranged adjacent the path of the chain and adapted to be struck or actuated when the chain exceeds a predetermined degree of slackness due to wear or other causes. In such devices the *operating force may consist merely of the weight of the chain as itlrests upon the actuating member, which may be insufficient'to effect the necessary adjustment of the chain. In other cases the actuating force may be exerted by means of a projection on the chain adapted to strike against the actuating member of the adjusting mechanism. In such cases a greater actuating force is available, but only instantaneously.

In either case there are obvious disadvantages, y

one of which is that, fora considerable period prior to the effective actuation of the adjusting mechanism, the chain or a projecting part thereof must run against or intermittently strike against the actuating member, causing considerable wear,

and possible breakage. Another disadvantage of such devices lies in the fact that the actuating force available has no particular relation to the force necessary to effect the chain tightening operation, and may be insufficient for the purpose.

It is an object of the present invention to provide chain adjusting mechanism which is positive in operation, and which employs an operating force considerably greater than that which is utilized by the prior art devices mentioned above.

A further object of the present invention is the provision of a chain adjusting device which is actuated whenever the chain exceeds a predetermined degree of slackness, the actuating member of which comprises a rotary member adapted to ride on the chain, in all conditions of the latter,

thus obviating the wear which is necessarily attendant upon the use of prior art adjusting de- 55 vices of the kind described above.

(CL 'i4-242.16)

A further object of the present invention is the provision of chain adjusting mechanism for use in connection with chains having a reach which becomes alternately slack and taut, which the force actuating the adjusting mechanism is that 5 which causes the chain to become taut after a slack period, such force being olf course proportional to that exerted bythe chain driven mechanism kand therefore proportional to the force necessary for effecting aV suitable adjustment of 10 thema n Other and further objects, featl'ires` and advantages of the present invention will be more apparent to those skilled in the art upon a consideration or the f ollowi'ngspecicati'on and accom- 15 panying drawing inv which:

Figure 1 is a side elevation, partly in section, of

a device constructed in accordance with the pres'- ent invention; and'y l Figure 2 is a horizontal section on line 2 2 of 20 Figure l.

In orderA to facilitate an understanding of the invention, reference isv made tothe embodiment thereof shown in the accompanying drawing and detailed descriptive language is employed. It will 25 nevertheless be understood that nov limitation of the invention isv thereby intended and that various changes and alterations are contemplated such as would ordinarily occur to one skilled in ther art to which theinvention relates. 30

For'purposesA oi illustration, the mechanism oi thev present Vinvention has been shown as applied to a ltype of mechanism commonly' employed for operating deepwell pumps. In'such-cases'the purnpdriving mechanism commonly derives its 35 power from a stationary engine, not shown, the power" beingv received at the pum-pdriving mechanism by a belt driven pulley 5; The latten is secured on a' shaft 6, journalled' in a suitable frame I. The pumping mechanism, represented in Figure 1 by a large sprocket wheel 8, is driven fromv the shaft 6 by means of a sprocket- Q'secured thereon, and a `sprocket chain I0. The remainder of the pumping mechanism forms no part ofthe present invention-I and will not be illustrated or described. However, it is to be noted that, due to the nature of the work done by the driving mechanism, the chainv I6 alternately exerts a driving force and a" resisting force on the sprocket wheel 8; so that the lower reach I0 of the chain 50 l0 (as well as the upper reach of the chain) become alternately taut and slack.

y In accordance with the present invention, the shaft 6 isjournalled in anti-frictionv bearings Il supported within*v eccentric cages I2, the latter being suitably journalled in the frame 1. Each of the eccentric cages I2 is provided with a toothed peripheral portion I3. A ratchet shaft I4 is journalled in the frame I adjacent the shaft 6 and has secured thereon a pair of spur gears i5 meshing with the toothed portions I3 of the eccentric cages I2. Likewise secured upon the shaft Iii is a ratchet I 6. A bifurcated arm I1 is pivoted on the shaft I4 and carries at its outer end an idler sprocket I8 which` is adapted to rest upon and mesh with the lower reach I0 of the chain II). Intermediate the ends of the arm I1 there is provided a pair of unstanding ears I9 carrying a pin 2S on which is pivoted a pawl ZI, the latter being adapted for engagement with the teeth of the ratchet I6. A detent 22, pivoted on a pin 23 suitably supported in the frame I, is normally held in engagement with the teeth of the ratchet I6 by a spring 2li and serves to restrain the ratchet I6 and its shaft I4 against clockwise movements.

As hereinbefore mentioned, the lower reach Ill of the chain Il] becomes alternately slack and taut, and the arm I7 and idler sprocket 18 are thereby caused to oscillate through a small arc about the shaft Ill. This normal oscillation of the arm I'I is not sufficient to cause the pawl 2| to fall over the edge of the tooth with which it is currently engaged, and the shaft I4 is therefore not rotated. As wear occurs in the chain I, or the latter becomes longer for any reason, the intermittent slackness of the lower reach I0' increases in extent. As soon as the slackness of the reach I increases to such` an extent that the pawl 2 I, during the slack period, is permitted to fall over the edge of the tooth with which it has been engaged, and thus to engage a new tooth, it is apparent that during the next taut period of the reach IU', the ratchet I6 and shaft I4 are rotated to the extent of one tooth. By this action, the detent 22 is raised and lowered into engagement with a new tooth, thus serving to retain the ratchet I8 and shaft I4 in the new position. As the shaft I4 rotates the spur gears I5, secured thereon, cause a corresponding rotation of the eccentric cages I2, thus moving the bearings II and shaft 6 a slight distance to the left and tightening the chain I0. This operation will be repeated whenever the slackness of the lower reach I of the chain exceeds a predetermined extent depending upon the size of the teeth of the ratchet I6.

It is apparent that the force which actuates the chain tightening mechanism is that which causes the reach I0 to become taut, and is proportional to the working force exerted by the pumping mechanism. Accordingly, the force actuating the chain tightening mechanism corresponds to that necessary to effect the chain tightening operation. The above described device is therefore positive in operation and will serve to maintain the chain Il] at the proper degree of tightness at all times.

Since the member which rides on the chain I0 is an idler sprocket and rotates freely in mesh with the chain I0, it does not add substantially to the amount of wear to which the chain is subjected. Because both ends of the sprocket shaft are shifted simultaneously and to the same eX- tent, there is no possibility of stressing the two sides of the chain unequally, with attendant disadvantages.

While the device of the present invention is particularly suited for chain drives having a variable load, as described, it may also be advantageously used with drives having a constant load, since nearly every such mechanism is stopped from time to time, for one reason or another. When stopped, the chain of course becomes slack, and if it is sumciently slack so that tightening is necessary, the pawl will engage a new tooth, and the tightening operation will take place when the drive is started up again. This mode of operation will be satisfactory since, in normal use, such drive chains require tightening only at infrequent intervals.

It will of course be obvious that in applying the present invention to a driving mechanism in which the sprocket shaft is disposed vertically and the chain moves in a horizontal plane, the idler sprocket I8 may be maintained in constant contact with the chain by means other than gravity.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In combination with chain-driven mechanism including a chain, a, frame, a sprocket shaft, means adjustably supporting said sprocket shaft in said frame, a sprocket on said shaft in driving engagement with said chain, means for actuating said supporting means to effect adjustment of said sprocket shaft relative to said frame, said actuating means comprising a member adapted to ride on a reach of said chain, and means connecting said member and said supporting means and adapted to actuate the latter whenever the slackness of said reach exceeds a predetermined extent.

2. In combination with chain-driven mechanism including a chain, a frame, a sprocket shaft, means adjustably supporting said sprocket shaft in said frame, a sprocket on said shaft in driving engagement with said chain, means for actuating said supporting means to effect adjustment of said sprocket shaft relative to said frame, `said actuating means comprising a rotatable ratchet, means operatively connecting said ratchet and said supporting means, a pivoted arm, a p-awl carried by said arm and havingv an operative engagement with said ratchet, and a member carried on the free end of said arm and adapted to ride on a reach of said chain, whereby said arm and pawl are caused to fall as said reach becomes slack and to be lifted by said reach as the latter becomes taut, said pawl being adapted to remain in engagement with the same tooth of said ratchet so long as the slackness of said reach remains within a predetermined limit.

3. In combination with the mechanism de-y fined in claim 2, means for preventing rotation of said ratchet in a direction to increase the slackness of said chain.

4. The combination defined in claim 2, said member comprising an idler sprocket journalledon said free end of said arm.

5. In combination with chain-driven mechanism including a chain, a frame, eccentric members journalled in said frame, said eccentric members having toothed portions, a sprocket' said arm and adapted to ride on a reach of saidy chain, whereby said arm and paWl are caused to fall as said reach becomes slack and to be lifted by said reach as the latter becomes taut, said pawl being adapted to remain in engagement with the same tooth of said ratchet so long as the slackness of said reach remains Within a predetermined limit.

6. In combination with chain-driven mechanism including a chain, a frame, a sprocket shaft, means adjustably supporting said sprocket shaft in said frame, a sprocket on said shaft in ber in constant contact With a reach of said l chain, and means connecting said member and said supporting means and adapted to actuate the latter Whenever the slackness of said reach exceeds a predetermined extent.

JOHN HART WILSON. 

